It's going to be a real toss up IMO, I'll assume that the room is long and not wide, with that in mind some height speakers may work (not if the room is wide) if you had some old speakers and some boxes around at least you could experiment with heights and some different positions. (Fronts, Rears even middles slightly behind the MLP labeled TM or TR) if you went with in-ceiling you'd want as wide of a dispersion as possible maybe even angle-able tweeters (to adjust where they fire as needed)
I use all height and think it works pretty well as an alternative to in-ceiling, but to be fair I have 9' ceilings and I don't know how much that plays in to the effect, but I'd absolutely choose them over Atmos enabled if that's what you were thinking.